This invention relates generally to thermal oxidative barrier coatings for organic matrix composites and to articles so coated.
Organic matrix composites (OMCs) are used in the aerospace industry for the weight reductions they offer when used to replace metal components. However, exposure to high temperature environments reduces mechanical properties and causes oxidative degradation of OMCs. Thus, even currently known high temperature OMCs utilizing high temperature matrix materials, such as PMR-15 and AFR-PE-4, have limited application.
One attempt to combat the problems in the art is to build thicker parts. However, the increased thickness adds weight and cost to the component as compared to what could be achieved if thermal and oxidative effects on the component were reduced.
Another attempt utilizes a sacrificial layer on the component to retard material degradation. The sacrificial layer may be a thin carbon veil impregnated with the PMC resin. However, the protection provided by the sacrificial layer is lost over time.
Currently, there are investigations into the use of ceramic fillers carried in polyimide matrices applied as a thermally sprayed coating for OMC components. The coating purports to improve the environmental durability and erosion resistance of the organic matrix composites. However, the thermal spraying process raises environmental, health, safety, energy, and labor issues. Additionally, it is difficult to provide a fully-cured coating system during a thermal spraying deposition process.
Accordingly, it would be desirable to improve the high temperature performance of components comprising organic matrix composites by providing a coating system that improves thermal oxidative stability and mechanical performance.